1. Field of the Invention
The present invention relates to a reader printer of the type in which the original images on a microfilm are projected onto a screen or a printer section.
2. Related Background Art
A typical reader printer comprises a projection optical system including a film illuminating section, a focusing lens and a plurality of fixed and movable mirrors. The respective movable mirrors are caused to displace and travel toward predetermined positions, thereby performing mutual switching between the reader mode and the printer mode of the reader printer and exposing a recording medium in a printer mechanism to a slit-shaped image projected thereon in the printer mode.
U.S. Pat. Nos. 4,367,033 and 4,589,767 disclose a typical form of projection system having the aforesaid arrangement. This arrangement includes three mirrors disposed on an image forming side of the focusing lens, the three microscope reflecting a portion of image forming light rays in the order of this arrangement so that an image in a slit-shaped portion of the original is formed onto a photosensitive medium (recording medium) in an exposure section. In this state, while the photosensitive medium is being caused to travel in the exposure section at an equal velocity, first and second ones of the three mirrors nearer the focusing lens are respectively caused to travel in predetermined directions, thereby exposing the photosensitive medium to the image projected thereon in a slit-like form.
However, the aforesaid type of projection system is arranged such that the first mirror directly opposing the focusing lens is scanned in parallel with and at 90 degrees with respect to the second mirror, and this may lead to various problems; for example, since the first mirror is unavoidably increased in size, the overall size of the system is correspondingly increased; it is necessary to employ a mirror having a reflection surface with high-precision flatness; and in addition, complicated adjustment is required to center the screen disposed in the reader mode optical path with respect to the photosensitive medium disposed in the printer mechanism.